*{
    margin: 0;
    padding: 0;
}
li{
    list-style-type: none;
}
a{
    text-decoration: none;
}
.left{
    width: 175px;
    height: 500px;
    /* border: 1px solid black; */
    position: fixed;
    top: 15px;
    left: 25px;
    z-index: 4;
}
.left h2{
    font-size: 20px;
    color: #000000;
    font-weight: 900;
}
.left .nav_item{
    width: 100%;
    height: auto;
}
.nav_item>h3{
    font-size: 11px;
    line-height: 20px;
    color: #000000;
}
.nav_item>.itembox{
    width: 100%;
    height: 0px;
    overflow: hidden;
    transition-property: height;
    transition-duration: 1s;
}
.nav_item:nth-of-type(4){
    margin-top: 32px;
}
.itembox ul{
    margin: 5px 0 5px 0;
}
.itembox ul li a{
    font-size: 11px;
    line-height: 15px;
    color: #000;
}
.nav_item:hover>.itembox{
    height: 210px;
}
.nav_item:nth-of-type(3):hover >.itembox{
    height: 100px;
}
.nav_item:nth-of-type(4):hover >.itembox,
.nav_item:nth-of-type(5):hover >.itembox,
.nav_item:nth-of-type(6):hover >.itembox{
    height: 150px;
}
.nav_item:nth-of-type(7):hover >.itembox{
    height: 50px;
}